Indoor trilateralization using digital off-air access units

ABSTRACT

A system for indoor localization using satellite navigation signals in a Distributed Antenna System. The system includes a plurality of Off-Air Access Units (OAAUs), each operable to receive an individual satellite navigation signal from at least one of a plurality of satellite navigation systems (e.g., GPS, GLONASS, Galileo, QZSS, or BeiDou) and operable to route signals optically to one or more DAUs. The system further includes a plurality of remote DRUs located at a Remote location that are operable to receive signals from a plurality of local DAUs. Moreover, the system includes an algorithm to delay each individual satellite navigation signal for providing indoor localization at each of the plurality of DRUs.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/199,617, filed Mar. 6, 2014; which claims priority to U.S.Provisional Patent Application No. 61/774,930, filed on Mar. 8, 2013,entitled “Indoor Trilateralization using Digital Off-Air Access Units”,the disclosure of which are hereby incorporated by reference in theirentirety for all purposes.

BACKGROUND OF THE INVENTION

An indoor positioning system (IPS) is a network of devices used tolocate objects or people inside a building. Currently, no standard foran IPS has been adopted in a widespread manner, adversely impactingdeployment.

An IPS typically relies on anchors with known positions rather thanrelying on satellites, since satellite signals are not typicallyavailable at indoor positions as a result of signal attenuationresulting from roofs and other building structures.

Despite the progress made in IPS design and implementation, there is aneed in the art for improved methods and systems related to indoorlocalization.

SUMMARY OF THE INVENTION

The present invention generally relates to wireless communicationsystems employing Distributed Antenna Systems (DAS) as part of adistributed wireless network. More specifically, the present inventionrelates to a DAS utilizing a digital Off-Air Access Unit (OAAU). In aparticular embodiment, the present invention has been applied to receiveGPS signals at the OAAUs that can be configured in a star configurationor a daisy chained configuration. In an embodiment, directional antennasare utilized at remote units for improving the accuracy of the indoorGPS position data. The methods and systems described herein areapplicable to a variety of communications systems including systemsutilizing various communications standards.

Satellite navigation systems, including the Global Positioning System(GPS) have received widespread use in many applications such as trafficmanagement, navigation, medical emergency services as well as locationbased services for handsets. GPS is discussed herein as an exemplarysatellite navigation system, although other systems, including GLONASS(Russian), Galileo (Europe), QZSS (Japanese), and BeiDou (Chinese) areincluded within the scope of the present invention and should beunderstood to fall under the umbrella of systems collectively referredto as GPS herein. Although GPS positioning is prevalent in outdoorapplications, indoor localization using GPS is not common because of thelarge signal attenuation caused by the building walls. Most indoorpositioning solutions require unique infrastructure that is complicatedand expensive to deploy. The indoor positioning architecture provided byembodiments of the present invention uses the existing GPS Satelliteinfrastructure and can be used with standard handsets that contain GPSreceivers.

A distributed antenna system (DAS) provides an efficient means ofdistributing signals over a given geographic area. The DAS networkcomprises one or more digital access units (DAUs) that function as theinterface between the Off-Air Access Units (OAAU) and the digital remoteunits (DRUs). The DAUs can be collocated with the Off-Air Access Units(OAAU). Under certain embodiments, the Off-Air Access Units may not becollocated with the DAUs. Off-Air Access Units can be used to relay GPSSatellite signals to one or more DAUs. Under certain embodiments theOff-Air Access Units may relay the GPS signals directly to one or moreDigital Remote Units (DRUs). One or more Off-Air Access Units can beused to communicate with one or more Satellites. The Off-Air AccessUnits relay the RF GPS signals between the Satellite and the coveragearea.

According to an embodiment of the present invention, a system for indoorlocalization using satellite navigation signals in a Distributed AntennaSystem is provided. The system includes a plurality of Off-Air AccessUnits (OAAUs). Each of the plurality of OAAUs is operable to receive anindividual satellite navigation signal from at least one of a pluralityof satellites and operable to route signals optically to one or moreDAUs. The systems also includes a plurality of remote DRUs located at aRemote location. The plurality of remote DRUs are operable to receivesignals from a plurality of local DAUs. The system further includes analgorithm to delay each individual satellite navigation signal forproviding indoor localization at each of the plurality of DRUs.

According to a specific embodiment of the present invention, a systemfor indoor localization using GPS signals in a Distributed AntennaSystem is provided. The system includes a plurality of Off-Air AccessUnits (OAAUs) operable to receive GPS signals from a plurality of GPSsatellites. The plurality of OAAUs are operable to route receivedsignals directly to one or more DRUs.

According to another specific embodiment of the present invention, asystem for indoor localization using GPS signals in a DistributedAntenna System includes a plurality of Off-Air Access Units (OAAUs)operable to receive GPS signals from a plurality of GPS satellites andoperable to route received signals optically to one or more local DAUs.A plurality of remote DRUs located at a Remote location, each havingmultiple directional antennas. The plurality of remote DRUs are operableto receive signals from the plurality of local DAUs. The system alsoincludes a de-multiplexer operable to extract one of the GPS signals andtime delay it at each of the plurality of remote DRUs and an algorithmoperable to determine a delay at each of the plurality of remote DRUsand to provide indoor localization information. The system furtherincludes a GPS receiver at the remote location used in a feedback loopwith each of the plurality of remote DRUs to control the delay.

Numerous benefits are achieved by way of the present invention overconventional techniques. Traditionally, an Off-Air GPS Repeatercommunicates with the satellite via a wireless RF signal andcommunicates with the coverage area via a wireless RF signal. Off-AirGPS repeaters broadcast the GPS Satellite signal indoors, which providesthe GPS Handset receiver with the position of the Off-Air Repeater. Insome embodiments, no additional intelligence is used to provide anypositional information for the location of the indoor user relative tothe Off-Air Repeater. An Off-Air Access Unit (OAAU) relays the GPSsignals to a DAU via an optical cable. The GPS signals from the Off-AirAccess Unit are transported digitally over an optical cable to one ormore DAUs or directly to one or more Digital Remote Units (DRU).Transporting the Off-Air Access Unit signals optically provides anadditional benefit of enabling time multiplexing of multiple GPS signalsfrom multiple Off-Air Access Units. Additionally, embodiments enable therouting of the Off-Air Access Unit signals to one or more remotelocations. Utilizing multiple GPS signals from multiple OAAUs canprovide enhanced indoor localization accuracy.

GPS positional information has a stringent requirement for accuracybecause First Response providers (911) need to quickly and accuratelylocate the position of the emergency. According to an embodiment of thepresent invention, a feedback mechanism is utilized to insure accuracyof the GPS positional information. The feedback mechanism involves theuse of a GPS receiver at the remote location in a closed loop with theDigital Remote Unit (DRU) broadcast of the Off-Air GPS signals. Anysignificant error between the DRU broadcast GPS position and the storedpredefined GPS position will result in an alarm. Thereby notifying theequipment maintenance staff of a problem. These and other embodiments ofthe invention along with many of its advantages and features aredescribed in more detail in conjunction with the text below and attachedfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the basic structure and an example ofthe transport routing based on having 3 GPS satellites with 3 DigitalAccess Units (DAUs) at a local location, 3 Off-Air Access Units (OAAUs)at a local location and Digital Remote Units (DRUs) at a remote locationaccording to an embodiment of the present invention. In this embodiment,3 OAAUs are connected to a DAU at the local location.

FIG. 2A is a block diagram showing the basic structure and an example ofthe transport routing based on having a 3 Satellites with 3 DAUs at alocal location, 3 OAAUs daisy chained together at a local location andoptical interfaces to DRUs at the remote locations according to anembodiment of the present invention.

FIG. 2B shows the data transport structure whereby the various SatelliteGPS signals are time-multiplexed into a frame according to an embodimentof the present invention.

FIG. 3 is a block diagram showing the basic structure and an example ofthe transport routing based on having multiple OAAUs at local locationswith multiple DAUs at a local location, and multiple Digital RemoteUnits (DRUs) at a remote location and optical interfaces to the Remotesaccording to an embodiment of the present invention.

FIG. 4 is a block diagram illustrating a DAU, which contains physicalNodes and a Local Router, according to an embodiment of the presentinvention.

FIG. 5 is a block diagram illustrating a Off-Air Access Unit (OAAU),which contains physical Nodes and a repeater router, according to anembodiment of the present invention.

FIG. 6 is a simplified flowchart illustrating the data flow structurebetween the Off-Air Access Unit (OAAU) and the DAU or another DRUaccording to an embodiment of the present invention.

FIG. 7 is a block diagram showing the basic structure and an example ofthe transport routing based on having multiple OAAUs at local locationswith multiple Digital Remote Units (DRUs) at a remote location andoptical interfaces to the Remotes according to an embodiment of thepresent invention.

FIG. 8 is a block diagram showing the basic structure and an example ofthe transport routing based on a single OAAU with 3 receivers at thelocal location with multiple DAUs at a local location, and multipleDigital Remote Units (DRUs) at a remote location and optical interfacesto the Remotes according to an embodiment of the present invention.

FIG. 9 is a conceptual building layout showing 3 OAAUs receiving the GPSsignals from a subset of Satellites and transporting those signals tothe Digital Remote Units (DRU) via optical cables according to anembodiment of the present invention. The remote signals at the DRUs arebroadcast over the antennas and received by the users' GPS receiver inthis embodiment.

FIG. 10 is a block diagram according to one embodiment of the inventionshowing the basic structure whereby the OAAU GPS signals on the Frameare time de-multiplexed, delayed relative to one another and thencombined according to an embodiment of the present invention.

FIG. 11 is a block diagram showing the basic structure whereby one ofthe OAAU GPS signals on the Frame is time de-multiplexed, delayed andthen transmitted at one or more DRUs according to an embodiment of thepresent invention. The GPS signals for the individual satellites aretransmitted on separate DRUs for the objective of replicating thesatellite configuration indoors in this embodiment.

FIG. 12 is a block diagram showing the basic structure whereby the OAAUGPS signals on the Frame are time de-multiplexed, delayed relative toone another and then combined according to an embodiment of the presentinvention. Each DRU is fed a distinct combination of Satellite GPSsignals in this embodiment.

FIG. 13 is a block diagram showing the DRU GPS transmitter in a feedbackloop that is driven by the error between the GPS Receiver position andthe predefined position that is stored on the server according to anembodiment of the present invention.

FIG. 14 is a block diagram showing the adaptive loop used to determinethe Delay values for the individual Satellite GPS signals according toan embodiment of the present invention. The position error resultingfrom the difference between the Measured GPS position and the predefinedGPS position is used to optimize the Delays for the various SatelliteGPS signals.

FIG. 15 is a block diagram showing the system configuration ofdirectional indoor antennas according to an embodiment of the presentinvention. As illustrated, each directional antenna is fed with a GPSsignal that corresponds to the same directional OAAU signal.

FIG. 16 is a block diagram showing the adaptive loop used to determinethe delay values for the individual Satellite GPS signals at the variousDRUs according to an embodiment of the present invention. The DRU feedsthe directional antennas with the GPS signals that correspond to thesame directional OAAU signal.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

A distributed antenna system (DAS) provides an efficient means oftransporting signals between local units and remote units. The DASnetwork comprises one or more digital access units (DAUs) that functionas the interface between the Off-Air Access Units (OAAU) and the digitalremote units (DRUs). The DAUs can be collocated with the Off-Air AccessUnits (OAAU). The DRUs can be daisy chained together and/or placed in astar configuration and provide coverage for a given geographical area.The DRUs are typically connected with the DAUs by employing a high-speedoptical fiber link. This approach facilitates transport of the RFsignals from the Off-Air Access Units (OAAU) to a remote location orarea served by the DRUs.

Off-Air Access Units communicate with one of more GPS Satellites overthe air. Off-Air Access Units are convenient for relaying GPS signalsbetween locations that are not well covered by the GPS Satellite itself.A typical Off-Air Access Unit receives the Downlink RF GPS signal from aSatellite, amplifies and filters the RF signal and transports it to aDRU for a given coverage area. Each Off-Air Access Unit utilizes adirectional antenna to communicate with a distinct subset of GPSSatellites. Typically, a minimum of 3 GPS Satellites are used totriangulate and determine the receiver's position. The relativetime-delays between the 3 GPS Satellites provide a means of identifyingthe 2D position of the receiver. 4 GPS Satellite signals will provide 3Dlocalization of the receiver. Directional antennas are used at theOff-Air Access Units in order to separate the 3 or more Satellitesignals. Each GPS Satellite signal will be time multiplexed in a datatransport frame structure and sent to the remote DRUs. It is assumedthat the DRUs position is known a-priori. The DRU's will receive theindependent GPS satellite signals, which are independently time-delayed,for example, by a user, in order to replicate the GPS position of theDRUs. The GPS positional information of each DRU can be determined froma 3D map of the given indoor venue. One embodiment of the presentinvention enables a GPS receiver to be incorporated in both the DRU aswell as the Off-Air Access Units. The absolute GPS position of the DRUscan be obtained be using the Off-Air Access unit GPS positioninformation and then adjusting it to the 3D position offset inside thevenue (e.g., 4^(th) floor, 30 m North, 10 m West). Locating a GPSreceiver at the DRU will provide a feedback mechanism of ensuring theaccuracy of the user-established time-delays in some embodiments.

FIG. 1 illustrates a DAS network architecture according to an embodimentof the present invention and provides an example of a data transportscenario between 3 GPS Satellites, multiple Off-Air Access Units(OAAUs), multiple local DAUs, and multiple DRUs. GPS Satellites 1,2 and3 are connected to OAAU 1 (120), OAAU 2 (121), and OAAU 3 (131),respectively, by wireless links in the illustrated embodiment. DAUs 1(102), (108) and DAU 3 (110) route the Off-Air Access Unit signals tothe various DRUs. Each of the local DAUs is connected to server (150).In this embodiment, the OAAUs are connected in a star configuration withDAU (102) using optical cables (i.e., optical fibers). Although threesatellites are illustrated in FIG. 1, the illustrated three satellitesare shown merely as an example and it will be appreciated thatadditional satellites (e.g., 4, 5, or more satellites) in theconstellation can be utilized by embodiments of the present invention.In the following figures, three exemplary satellites are illustrated,but the embodiments illustrated in the following figures are not limitedto the use of only three satellites. One of ordinary skill in the artwould recognize many variations, modifications, and alternatives.

One feature of embodiments of the present invention is the ability toroute the GPS Satellite signals among the DAUs (102, 108, 109) and DRUs(105). In order to route GPS signals available from one or moreSatellites, it is desirable to configure the individual router tables ofthe DAUs and DRUs in the DAS network. This functionality is provided byembodiments of the present invention.

The DAUs (102, 108, 109) are networked together to facilitate therouting of signals among multiple DAUs. This architecture enables thevarious GPS Satellite signals to be transported simultaneously to andfrom multiple DAUs. PEER ports are used for interconnecting DAUs in someimplementations.

The DAS network can include a plurality of OAAUs, DAUs (102, 108, 109)and DRUs (105). The DAU (102) communicates with the network of DRUs(105) and the DAU (102) sends commands and receives information from theDRUs. The DAUs (102, 108, 109) include physical nodes that accept anddeliver RF signals and optical nodes that transport data. A DAU caninclude an internal server or an external server. An external server(150) is shown in FIG. 1. The server is used to archive information in adatabase, store the DAS network configuration information, and performvarious data related processing among other functions.

Additionally, the OAAU (120, 121, 131) communicates with the DAU (102).The OAAU (120, 121, 131) receives commands from the DAU (102) anddelivers information to the DAU (102). The OAAUs (120, 121, 131) includephysical nodes that accept GPS RF signals and optical nodes thattransport data.

As shown in FIG. 2A, the individual GPS signals from Satellites SAT 1,SAT 2 and SAT 3 are transported to a daisy-chained network of OAAUs(220, 221, 222). FIG. 2 demonstrates how three independent Satellites,each Satellite communicating with an independent OAAU, provide inputinto a single DAU (202). A server (240) is utilized to control therouting function provided in the DAS network. Referring to FIG. 2A andmerely by way of example, DAU 1 (202) receives downlink GPS signals fromthe daisy-chained network of OAAUs (220, 221, 222). OAAU 1 (220)translates the RF signals to optical signals for the downlink. Theoptical fiber cable (224) transports the SAT 1 signals between OAAU 1(220) and OAAU 2 (221). The optical signals from OAAU 1 (220) and OAAU 2(221) are multiplexed on optical fiber (225). The other OAAUs in thedaisy chain are involved in passing the optical signals onward to DAU 1(202). DAU 1 (202) DAU 2 (208) and DAU 3 transport the optical signalsto and from the network of DRUs (205). As shown in FIG. 2B, the variousGPS signals from the Satellites are time multiplexed into a data stream(600) for transporting throughout the DAS network. Another embodiment ofthe present invention includes the use of RF connections between theOAAUs and the DAUs. In this embodiment the OAAU will receive the RFsignals from the GPS Satellite and transport the RF signal to a DAUusing an RF cable.

FIG. 3 depicts a DAS system employing multiple Off-Air Access Units(OAAUs) (321, 331, 341) at the local location and multiple DigitalRemote Units (DRUs) (305) at the remote location. In accordance with theillustrated embodiment, each DRU (304, 306, 307) provides uniqueinformation associated with each DRU, which uniquely identifies datareceived by a particular Digital Remote Unit. In this embodiment, theindividual OAAUs are independently connected to DAUs (302, 308, N).Another embodiment of the present invention includes the use of RFconnections between the OAAUs and the DAUs. In this alternativeembodiment the OAAU will receive the RF signals from the GPS Satelliteand transport the RF signal to a DAU using an RF cable.

The servers illustrated herein, for example, server (350) provide uniquefunctionality in the systems described herein. The following discussionrelated to server (350) may also be applicable to other serversdiscussed herein and illustrated in the figures. Server (350) can beused to set up the switching matrices to allow the routing of signalsbetween the remote DRUs. The server (350) can also store configurationinformation, for example, if the system is powered down or one DRU (306)or one OAAU (321) goes off-line and then the system is powered up, thesystem will typically need to be reconfigured. The server (350) canstore the information used in reconfiguring the system and/or the DRUs,OAAUs or DAUs.

FIG. 4 shows two of the elements in a DAU, the Physical Nodes (400) andthe Local Router (401). The Physical Nodes (400) translate the RFsignals to baseband for the Downlink. The local Router (401) directs thetraffic between the various LAN Ports (403), PEER Ports (415) and theExternal Ports (409, 410). The physical nodes can connect to the OAAUsat radio frequencies (RF). The physical nodes can be used for differentSatellite connections.

FIG. 4 shows an embodiment whereby the physical nodes (400) haveseparate inputs for the downlink paths (404). The physical node (400)translates the signals from RF to baseband for the downlink path. Thephysical nodes (400) are connected to a local Router (401) via externalports (409,410)). The local router (401) directs the uplink data streamfrom the LAN Ports (403) and PEER ports (415) to the selected External Uports (410). Similarly, the router directs the downlink data stream fromthe External D ports (409) to the selected LAN Ports (403) and PEERports (415).

In one embodiment, the LAN Ports (403) and PEER ports (415) areconnected via an optical fiber to a network of DAUs and OAAUs. Thenetwork connection can also use copper interconnections such as CAT 5 or6 cabling, or other suitable interconnection equipment. The DAU is alsoconnected to the internet network using IP (406). An Ethernet connection(408) is also used to communicate between the Host Unit (402) and theDAU. The DRU and OAAU can also connect directly to the RemoteOperational Control center (407) via the Ethernet connection (408).

FIG. 5 shows two of the elements in an OAAU, the Physical Nodes (501)and the Repeater Router (500). The OAAU includes both a Repeater Router(500) and Physical Nodes (501). The Repeater Router (500) directs thetraffic between the LAN ports (502), External Ports (506, 507) and PEERPorts (515). The physical nodes (501) connect wirelessly to the GPSSatellite at radio frequencies (RF). The physical nodes (501) can beused for different Satellites, different antennas, etc. FIG. 5 shows anembodiment whereby the physical nodes (501) have separate outputs forthe downlink paths (503). The physical node (501) translates the signalsfrom RF to baseband for the downlink path. The physical nodes areconnected to a Repeater Router (500) via external ports (506,507). Therepeater router (500) directs the downlink data stream from the LANports (502) and PEER ports (515) to the selected External D ports (506).The OAAU also contains an Ethernet Switch (505) so that a remotecomputer (509) or wireless access points (520) can connect to theinternet.

FIG. 6 is a simplified flowchart illustrating a method of routing GPSsignals from the various Satellites to each DRU according to anembodiment of the present invention. As shown in block (619), the timemultiplexed GPS signals (616) from the respective Satellites are timedelay offset to replicate the GPS position of the respective DRU. TheDRU then broadcasts the GPS signal for detection by the users'equipment.

As shown in FIG. 7, the individual GPS signals from Satellites SAT 1,SAT 2 and SAT 3 are transported to a daisy-chained network of OAAUs(720, 721, 722). FIG. 7 demonstrates how three independent Satellites,each Satellite (SAT 1, SAT 2, SAT 3) communicating with an independentOAAU (722, 721, 720 respectively), provide input into a single DRU(702). A server (740) is utilized to control the routing functionprovided in the DAS network. Referring to FIG. 7 and merely by way ofexample, DRU 1 (702) receives downlink GPS signals from thedaisy-chained network of OAAUs (720, 721, 722). OAAU 1 (720) translatesthe RF signals to optical signals for the downlink. The optical fibercable (724) transports the SAT 1 signals between OAAU 1 (720) and OAAU 2(721). The optical signals from OAAU 1 (720) and OAAU 2 (721) aremultiplexed on optical fiber (725). The other OAAUs (722) in the daisychain are involved in passing the optical signals onward to DRU 1 (702).DRU 1 (702), DRU 2 (703) and DRU 3 (704) transport the optical signalsto and from the network of DRUs in a daisy chain configuration.

As shown in FIG. 8, the individual GPS signals from Satellites SAT 1,SAT 2 and SAT 3 are transported to a single OAAU, a multiple inputoff-air access unit (MIOAAU) (820), with multiple directional antennas(851, 852, 853). FIG. 8 demonstrates an architecture in which threeindependent Satellites are utilized, each Satellite communicating withan independent RF receiver in the MIOAAU (820). The MIOAAU (820)time-multiplexes the independent GPS signals to the DAS network as shownin FIG. 8. In some embodiments, a plurality of MIOAAUs can transmit theindependent GPS signals to the DAS network.

FIG. 9 shows an embodiment of the system used in a three level building(900). The present invention is not limited to three levels and can beapplied to buildings with additional or fewer levels. The Off-Air AccessUnits (921, 922, 923) are located on the roof of the building and inline of sight of the Satellites (911, 912, 913). Directional antennas(901, 902, 903) are used at the OAAUs (921, 922, 923) in order to limitthe number of Satellite GPS signals captured by each OAAU. The objectiveis to separate the Satellite GPS signals at each OAAU. The GPS signalsare multiplexed on the optical fiber (941), (942) and transported to DRU1 (931) and DRU 2 (932). The GPS signals are de-multiplexed at each DRUand combined to create the position at the respective DRU. The signalsare broadcast through the RF antennas (950) connected via RF cables(951, 952) to the DRUs (931, 932). GPS Device (962) receives the signalbroadcast from DRU 2 (932) that identifies the DRU's position.

As shown in FIG. 10, the GPS Satellite down stream data (1000) isde-multiplexed and each respective GPS signal (1010, 1011, 1012) is timedelayed (1020, 1021, 1022) and summed (1030) in order to simulate theposition of the DRU. Each DRU transmits the GPS position at therespective DRU. The accuracy of the positional information at the users'GPS device is a function of the proximity to the DRU.

As shown in FIG. 11, the GPS Satellite down stream data (1100) isde-multiplexed and each DRU (1132, 1133, 1134) time delays (1120, 1121,1122) and transmits one or more of the respective GPS signals (1110,1111, 1112). This embodiment enables triangulation at the users' GPSdevice (1142) by replicating the Satellite signals (1152, 1153, 1154)indoors.

As shown in FIG. 12, the GPS Satellite down stream data (1200) isde-multiplexed and each DRU (1232, 1233, 1234) time delays (1220) andtransmits one or more of the respective GPS signals (1210, 1211, 1212).Each OAAU focuses on a distinct set of satellites. In this embodiment,three distinct satellite GPS signals (1210, 1211, 1212) are received ateach of the OAAU and there are three OAAUs. Each DRU (1232, 1233, 1234)transmits a unique set of Satellite GPS signals (1210, 1211, 1212). Thisembodiment enables triangulation at the users' GPS device (1242) byproviding three unique GPS locations at the three DRUs (1232, 1233,1234). The users' GPS device will average the three GPS positions toobtain a more accurate position of the users' location.

The position of a GPS receiver is determined by knowing its latitude,longitude and height. Four measurements are typically used to determinethe latitude, longitude, height and eliminate the receiver clock error.The GPS receiver has embedded software that has an algebraic model thatdescribes the geometrical position. For each measurement an equation ofthe distance to the satellite, p, can be written that is a function ofthe satellite position (x,y,z), the GPS receiver position (X,Y,Z) andthe clock error. For simplicity, the clock error has been removed fromeach equation below, since it is common to all equations.

p _(1k)=√{square root over (X−x ₁+Δ_(1k))²+(Y−y ₁+Δ_(2k))²+(Z−z₁+Δ_(3k))²)}

p _(2k)=√{square root over (X−x ₂+Δ_(1k))²+(Y−y ₂+Δ_(2k))²+(Z−z₂+Δ_(3k))²)}

p _(3k)=√{square root over (X−x ₃+Δ_(1k))²+(Y−y ₃+Δ_(2k))²+(Z−z₃+Δ_(3k))²)}

□

p _(Nk)=√{square root over (X−x _(N)+Δ_(1k))²+(Y−y _(N)+Δ_(2k))²+(Z−z_(N)+Δ_(3k))²)}

where (X,Y,Z) is the position of the OAAU and (x_(N),y_(N),z_(N)) is theposition of Satellite N. and (Δ_(1k),Δ_(2k),Δ_(3k)) are the calculatedpositional offsets for DRU k.The position of DRU k is at (X+Δ_(1k),Y+Δ_(2k), Z+Δ_(3k)).The set of four or more equations is solved simultaneously to obtain thevalues for the OAAU position (X,Y,Z). The Cartesian coordinates can beconverted to latitude, longitude, and height in any geodetic datum. Ingeneral, a procedure known as the Newton-Raphson iteration is used. Inthis procedure, each of the equations is expanded into a polynomialbased on an initial guess of the OAAU position. Iteratively the fourequations are solved simultaneously. If either one of the height,latitude or longitude is known then only three equations are typicallyused to resolve for the OAAU position.

The calculated positional offsets, Δ's, for each DRU can be obtainedfrom the blueprints of the venue and the location of the DRU in thevenue. The positional offsets are converted into time delays by dividingby the speed of light. The time delays are applied to signals (x₁,y₁,z₁)as shown in FIG. 10 (1020, 1021, 1022). The resultant signal istransmitted at the DRU and subsequently received by the GPS device.

In some embodiments, the DAU is connected to a host unit/server, whereasthe OAAU does not connect to a host unit/server. In these embodiments,parameter changes for the OAAU are received from a DAU, with the centralunit that updates and reconfigures the OAAU being part of the DAU, whichcan be connected to the host unit/server. Embodiments of the presentinvention are not limited to these embodiments, which are described onlyfor explanatory purposes.

FIG. 13 shows the adaptive GPS repeater system (1302) that includes aGPS receiver (1350) at the remote location along with the Digital RemoteUnit (DRU) (1300). The DRU (1300) contains an Up-Converter (UPC) (1340)which frequency translates the baseband signals (1330) to RF signals(1345). The function of the GPS receiver (1350) is to ensure that theinformation being transmitted by the DRU (1300) is accurate. Thisprovides a safety mechanism, whereby, if there is a significant errorbetween the transmitted GPS positional information and the predefinedGPS an alarm will be sent. The predefined GPS position will beestablished in the provisioning of the system and stored on the server(1380) as well as in the DRU (1300). The adaptive algorithm (1360) isused to adjust the Delay values (1320,1321,1322) of the GPS Satellitesignals (1310,1311,1312). The Microprocessor (1370) in the DRU controlsthe adaptive algorithm (1360). In one embodiment of this invention, theGPS receiver (1350) can be strictly a software program rather thanneeding to translate the baseband DRU signal to RF and then input thesignal into the RF receiver front end (1351) of the GPS receiver (1350).

FIG. 14 shows a block diagram of the Feedback system used to control theSatellite GPS signal Delays (1420,1421,1422). The GPS receiver measuresthe transmitted GPS signal from the DRU and determines the position(Latitude, Longitude, Height) in block (1430). This position is comparedto the known GPS position (1450) that was established duringprovisioning. The resultant position error (1440) is used to drive anadaptive algorithm (1460) such as the Least Mean Squared (LMS)algorithm. The Delays (1420,1421,1422) are adjusted to minimize theresultant position error (1440). In the event that the position error isabove a predefined threshold, then an alarm (1470) is activated. Thismechanism also serves as a means of calibrating the delays(1420,1421,1422) at the time of provisioning. In one embodiment of theinvention, once the delays (1420,1421,1422) have been determined thenthey can be stored in the DRU and the server and no further adaptationis required.

As shown in FIG. 15, the GPS Satellite down stream data isde-multiplexed at each DRU (1513). The DRUs (1531, 1532, 1533, 1534)time delay (1511) and transmit (1512) one or more of the respective GPSsignals (1510). Each OAAU focuses on a distinct set of satellites usingdirectional antennas. In this embodiment, four distinct satellite GPSsignals (1510) are received at each of the OAAU. In this embodiment, theOAAU has directional antennas pointing at a specific region in the sky.The objective is for the OAAU directional antennas to minimize theoverlap of satellite signals and, at the same time, ensure that asufficient number of satellites are measured. Satellite signals from asufficient number of satellites will enable the determination ofaccurate positional information. Each DRU receives the same set ofSatellite GPS signals (1510). The DRU's directional antennas (1514)transmit the Satellite GPS signals corresponding to the same directionas the received OAAU GPS signal. For example, a North facing OAAUantenna will correspond to a North facing indoor DRU directional antenna(1515). The adaptive loop is used to set and maintain the delays thatwill provide the accurate GPS signals corresponding to the respectiveDRU. This embodiment enables the GPS device (1542) to receive GPSsignals (1510) from multiple DRUs. As depicted in FIG. 15, the userdevice (1542) will receive a signal from the surrounding DRUs. Thevarious GPS signals, from each of the surrounding DRUs (1531, 1532,1533, 1534), will be delayed by the propagation distances (1541, 1542,1543, 1544) between the DRUs and the user. The propagation distances(1541, 1542, 1543, 1544) or corresponding propagation time delays ofeach of the respective GPS satellite signals will provide an enhancedaccuracy of the users' position. The objective is to provide anapproximation for the Satellite positions indoors using multiple DRUs(1531, 1532, 1533, 1534).

FIG. 16 shows a block diagram whereby the delay values (1620, 1621,1622, 1623) are optimized to best approximate the position of therespective DRU. Each of the GPS Satellite signals is combined (1680) soas to realize the GPS position (1630) of the DRU. However, each of theGPS Satellite signals will be transmitted through an independentdirectional antenna (1690). In this embodiment 4 directional antennasare used, however the concept can be extended to 3,4 or more directionalantennas. The DRU's directional antennas (1690) transmit the SatelliteGPS signals corresponding to the same direction as the received OAAU GPSsignal.

It is also understood that the examples and embodiments described hereinare for illustrative purposes only and that various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of this applicationand scope of the appended claims.

1. A system for indoor localization using satellite navigation signalsin a Distributed Antenna System, the system comprising: a plurality ofOff-Air Access Units (OAAUs), each having at least one directionalantenna and each being operable to receive at least one of a pluralityof satellite navigation signals from a plurality of satellites; one ormore Digital Access Units (DAUs), wherein the plurality of OAAUs arecommunicatively coupled to at least one of the one or more DAUs; and aplurality of Digital Remote Units (DRUs) located at a remote location,wherein each individual DRU of the plurality of DRUs is operable to:receive one or more of the plurality of satellite navigation signalsfrom the one or more DAUs; delay the one or more of the plurality ofsatellite navigation signals based on a positional offset for theindividual DRU; and broadcast, using an antenna of the individual DRU,the delayed one or more of the plurality of satellite navigationsignals.
 2. The system of claim 1, further comprising: a feedback systemcommunicatively coupled to a first DRU of the plurality of DRUs; and aGPS receiver at the remote location communicatively coupled to thefeedback system, wherein the GPS receiver transmits a measured GPSposition to the feedback system.
 3. The system of claim 2, wherein theone or more satellite signals are delayed further based on a differencebetween the measured GPS position and a known position of the GPSreceiver.
 4. The system of claim 1, wherein the positional offset forthe individual DRU is based on a position of the individual DRU withinthe remote location.
 5. The system of claim 1, wherein the plurality ofsatellite navigation signals include at least one of GPS, GLONASS,Galileo, QZSS, or BeiDou signals.
 6. The system of claim 1, wherein theone or more DAUs are coupled via at least one of a Ethernet cable,Optical Fiber, or Wireless Link.
 7. The system of claim 1, wherein theplurality of OAAUs are connected to the one or more DAUs via at leastone of Ethernet cable, Optical Fiber, or Wireless Link.
 8. The system ofclaim 1, wherein the plurality of OAAUs are connected together via adaisy chain configuration.
 9. The system of claim 8, wherein theplurality of OAAUs are coupled via at least one of Ethernet cable,Optical Fiber, or Wireless Link.
 10. The system of claim 1, wherein amobile device at the remote location is configured to receive thedelayed one or more of the plurality of satellite navigation signals.11. A method for indoor localization using satellite navigation signals,the method comprising: receiving, by a plurality of Off-Air Access Units(OAAUs) each having at least one directional antenna, a plurality ofsatellite navigation signals from a plurality of satellites; receiving,by one or more Digital Access Units (DAUs), the plurality of satellitenavigation signals from the plurality of OAAUs; for each individualDigital Remote Unit (DRU) of a plurality of DRUs located at a remotelocation: receiving one or more of the plurality of satellite navigationsignals from the one or more DAUs; delaying the one or more of theplurality of satellite navigation signals based on a positional offsetfor the individual DRU; and broadcasting, using an antenna of theindividual DRU, the delayed one or more of the plurality of satellitenavigation signals.
 12. The method of claim 11, wherein a feedbacksystem communicatively coupled to a first DRU of the plurality of DRUs,and wherein the method further comprises: measuring, by a GPS receiverat the remote location, a GPS position; and transmitting, by the GPSreceiver, the measured GPS position to the feedback system.
 13. Themethod of claim 12, wherein the one or more satellite signals aredelayed further based on a difference between the measured GPS positionand a known position of the GPS receiver.
 14. The method of claim 11,wherein the positional offset for the individual DRU is based on aposition of the individual DRU within the remote location.
 15. Themethod of claim 11, wherein the plurality of satellite navigationsignals include at least one of GPS, GLONASS, Galileo, QZSS, or BeiDousignals.
 16. The method of claim 11, wherein the one or more DAUs arecoupled via at least one of a Ethernet cable, Optical Fiber, or WirelessLink.
 17. The method of claim 11, wherein the plurality of OAAUs areconnected to the one or more DAUs via at least one of Ethernet cable,Optical Fiber, or Wireless Link.
 18. The method of claim 11, wherein theplurality of OAAUs are connected together via a daisy chainconfiguration.
 19. The method of claim 18, wherein the plurality ofOAAUs are coupled via at least one of Ethernet cable, Optical Fiber, orWireless Link.
 20. The method of claim 11, wherein a mobile device atthe remote location is configured to receive the delayed one or more ofthe plurality of satellite navigation signals.